Adjustable stop for check valve

ABSTRACT

A check valve comprises a housing, a fluid passage, a seat, a valve member and a stop. The fluid passage extends through the housing. The seat is disposed in the fluid passage. The valve member is positioned in the passage to engage the seat. The stop extends through the housing to engage the valve member. The stop is accessible from outside the housing to adjust a distance the valve member can travel from the seat. In one embodiment, the stop includes a variable stop feature, such as an offset pin or a cam. In another embodiment, the stop includes a pump control valve. In yet another embodiment, the housing includes markings to indicate a position of the stop. The valve member comprises a ball or a poppet in different embodiments.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority as a divisional application under 35U.S.C. §121 of earlier filed U.S. Non-Provisional application Ser. No.14/370,177 filed on Jul. 1, 2014, and entitled “ADJUSTABLE STOP FORCHECK VALVE,” which claimed priority as a national stage applicationunder 35 U.S.C. §371 to earlier filed PCT Application No.PCT/US2012/069780 filed on Dec. 14, 2012, and entitled “ADJUSTABLE STOPFOR CHECK VALVE,” which claimed priority to earlier filed U.S.Provisional Application No. 61/570901 filed on Dec. 15, 2011, andentitled “ADJUSTABLE PRESSURE CONTROL USING VARIABLE INLET BALL TRAVEL.”

BACKGROUND

The present disclosure relates generally to valves for fluid pumpingsystems. More particularly, the present disclosure relates to adjustablestops for check valves.

Fluid pumping systems are typically used to pressurize materials thatare applied using various spray systems. A single spray system can beused to dispense a variety of fluids, such as paints, varnishes,textured coatings, solvents, epoxies, polyurethane and the like. Each ofthese fluids has a different viscosity, which affects the quality of thesprayed fluid and the efficiency of the pumping system. It is,therefore, desirable to adjust settings of the spray system toaccommodate the viscosities of different fluids. One such setting is theopening size at the low pressure inlet of the pump, which is typicallydetermined by an inlet check valve. Thick fluids require large inletopenings to permit a sufficient volume of fluid through the inlet. Inletopenings that are too small for a thick fluid can cause undesirablesuction to form in the pump if the fluid cannot enter the inlet fastenough. Thin fluids only require small inlet openings to properly primethe pump and to run efficiently. Too much travel of the ball may causewear of the ball and ball seat due to excess inertia of the ball, andmay reduce pump efficiency. In conventional spray systems, adjustment ofthe inlet opening requires disassembly of the spray system. For example,U.S. Pat. No. 7,025,087 to Weinberger et al. discloses an inlet ballvalve having shims that change the inlet opening size. In order to addor remove shims, however, the pump must be disassembled, which isinconvenient and inefficient. There is, therefore, a need for a moreexpedient inlet opening adjustment mechanism.

SUMMARY

The present disclosure is directed to a check valve for a pump. Thecheck valve comprises a housing, a fluid passage, a seat, a valve memberand a stop. The fluid passage extends through the housing from a firstend to a second end. The seat is disposed in the fluid passage betweenthe first and second ends. The valve member is positioned in the passageto engage the seat. The stop extends through the housing to engage thevalve member. The stop is accessible from outside the housing to adjusta distance the valve member can travel from the seat. In one embodiment,the stop includes a variable stop feature, such as an offset pin or acam. In another embodiment, the stop includes a pump control valve. Inyet another embodiment, the housing includes markings to indicate aposition of the stop. The valve member comprises a ball or a poppet indifferent embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a fluid dispensing device having an inletvalve with a first embodiment of an adjustable ball stop.

FIG. 2 is an exploded view of the dispenser of FIG. 1 showing theadjustable ball stop, the inlet check valve, a pump valve and a controlknob.

FIG. 3 is a close-up view of the pump valve inserted into a slot of theadjustable ball stop, and the adjustable ball stop and inlet check valveinserted into sockets in the housing.

FIG. 4 is a cross-sectional view of a second embodiment of an adjustableball stop comprising a detent set-point rod.

FIG. 5 is a perspective view of the adjustable ball stop of FIG. 4showing the detent set-point rod inserted into a ball valve housing.

FIG. 6 is a cross-sectional view of a third embodiment of an adjustableball stop comprising a threaded set-point rod.

FIG. 7 is a cross-sectional view of a fourth embodiment of an adjustableball stop comprising a rotatable ball stop.

FIGS. 8A-8C show a first embodiment of the rotatable ball stop of FIG. 7comprising an offset pin.

FIGS. 9A-9C show a second embodiment of the rotatable ball stop of FIG.7 comprising a cam.

FIG. 10 is a cross-sectional view of a fifth embodiment of an adjustableball stop comprising a push-pull bar.

FIG. 11 is a cross-sectional view of a sixth embodiment of an adjustableball stop having a cartridge with a detent position control.

FIG. 12 is a top view of the cartridge of FIG. 11 showing differentdetent holes.

DETAILED DESCRIPTION

FIG. 1 is a schematic view of fluid dispensing device 10 having inletvalve 12 with a first embodiment of adjustable stop 14. Fluid dispensingdevice 10 also includes drive element 16, pumping mechanism 18, pumpvalve 20 and spray tip assembly 22. Drive element 16 provides power topumping mechanism 18, which draws fluid into housing 24 at inlet tube 26from a fluid container (not shown). Pumping mechanism 18 pressurizes thefluid and pumps it to outlet 28, which is fluidly coupled to spray tipassembly 22. Spray tip assembly 22 is user-actuated to permitpressurized fluid through orifice 30, which atomizes the fluid forspraying.

Drive element 16 comprises a mechanism or motor for producing rotationof drive shaft 32. In the embodiment shown, drive element 16 comprisesan electric motor. In other embodiments, drive element 16 may comprise apneumatic motor. Pumping mechanism 18 comprises a dual piston pump. Inother embodiments, pumping mechanism 18 may comprise adouble-displacement single piston pump, a gerotor (generated rotor), agear pump or a rotary vane pump. Pumping mechanism 18 includes shaft 34,which is coupled to shaft 32 of drive element 16 through gear system 36.For example, gears 38, 40, 42 and 44, and shaft 46 provide a gearreduction means that slows the input to shaft 34 from the input providedby shaft 32. Specifically, shaft 32 rotates gear 38, which is engagedwith gear 40 to rotate shaft 46. Shaft 46 rotates gear 42, which drivesshaft 34 through gear 44. Rotation of shaft 34 produces wobble of hub48. Operation of hub 48 is described further in U.S. Pat. App. Pub. No.2012/0037726 to Johnson et al., which is assigned to Graco MinnesotaInc. and is incorporated by this reference.

Pistons 50 and 52 engage hub 48 such that wobble of hub 48 producesreciprocating motion of pistons 50 and 52. Piston 50 is disposed withincylinder 54 and piston 52 is disposed within cylinder 56. On a backstroke, piston 50 retreats within cylinder 54 via coupling to hub 48 todraw fluid from inlet tube 26 into cylinder 54 through port 57, whilepiston 52 simultaneously is pushed forward via engagement with hub 48 topush fluid from cylinder 56 and chamber 58 into outlet 28. On a forwardstroke, piston 50 moves forward via coupling to hub 48 to push fluidfrom cylinder 54 into chamber 58 and cylinder 56 through porting inhousing 24 (not shown), while piston 52 simultaneously is pushedbackward via pressure within chamber 58 as fluid travels from chamber 58into cylinder 56. To accommodate such volumetric flows, piston 50 has adisplacement volume sufficient to fill both cylinder 56 and chamber 58.Pump valve 20 prevents fluid within chamber 58 from back flowing intocylinder 54. Inlet valve 12 prevents fluid within cylinder 54 from backflowing into inlet tube 26. Pressurized fluid from outlet 28 flows intospray tip assembly 22, which includes actuation needle 60 that can beselectively actuated to allow pressurized fluid to flow through orifice30. Operation of spray tip assembly 22 is described further in U.S. Pat.App. Pub. No. 2011/0198413 to Thompson et al., which is assigned toGraco Minnesota Inc. and is incorporated by this reference.

Fluid dispensing device 10 is configured to be able to spray fluidshaving different viscosities, fluids that are thick and fluids that arethin. For example, device 10 may spray thick fluids such as coatings orepoxies, and device 10 may be configured to spray thin fluids, such aspaint and varnishes. Adjustable stop 14 is adjusted in order toconfigure device 10 for different fluids by changing the amount thatinlet check valve 12 is permitted to open. Adjustable stop 14 includesrod 62 and knob 64. Inlet check valve 12 includes spring 66, ball 68,seat 70 and collar 72, which are shown and discussed in greater detailwith reference to FIGS. 2 and 3.

FIG. 2 is an exploded view of dispenser 10 of FIG. 1 showing adjustablestop 14 and inlet check valve 12. Dispenser 10 includes housing 24 andpump valve 20. Adjustable stop 14 includes adjustment rod 62 and knob64. Inlet check valve 12 includes spring 66, ball 68, seat 70 and collar72. Pump valve 20 includes body 74, spring 76, ball 78 and seat 79.Adjustment rod 62 of adjustable stop 14 includes stem 80, tube 82,channel 84, windows 86 and inlets 88. Housing 24 includes socket 90,inlet passage 92, and socket 94, which fluidly connects to inlet tube 26(FIGS. 1 & 3). When assembled, inlet check valve 12 controls fluid flowfrom inlet tube 26 to channel 84 through inlet passage 92, while pumpvalve 20 controls fluid flow from channel 84 to outlet 28 throughwindows 86. Specifically, knob 64 is rotated to thread adjustment rod 62in and out of socket 90 to change the distance between stem 80 and seat70, while pump valve 20 rides along inside channel 84. Knob 64 includesmarkings 95 that provide an indication of the position of stem 80relative to seat 70 or that provide an indication of the type, e.g.viscosity, of fluid that system 10 is configured to spray.

FIG. 3 is a close-up view of pump valve 20 inserted into channel 84 ofadjustment rod 62, adjustable stop 14 inserted into socket 94 in housing26, and inlet valve 12 inserted into socket 94 of housing 26. Whenassembled, body 74 of pump valve 20 is inserted into channel 84 suchthat spring 76 biases ball 78 against seat 79. In one embodiment, body74 is threaded into channel 84. As such, fluid is prevented from passingbetween inlets 88 and windows 86 by ball 78. Adjustment rod 62 isinserted into socket 90 such that stem 80 is inserted into inlet passage92. In one embodiment, adjustment rod 62 is threaded into socket 90.Inserted as such, windows 86 in tube 82 allow cylinder 54 to fluidlycommunicate with outlet 28 via channel 84. Seal 96A prevents fluidbetween tube 82 and body 74 from escaping channel 84, and seals 96B and96C prevent fluid between housing 24 and tube 82 from escaping socket90. Stem 80 extends through inlet passage 92 to engage ball 68.

Seat 70 is disposed within a counterbore in inlet tube 26. Inlet tube 26is inserted into socket 94 such that ball 68 is positioned between seat70 and stem 80. In one embodiment, inlet tube 26 is threaded into socket94. Collar 72 is disposed within socket 94 and surrounds ball 68. Spring66 is disposed within inlet passage 92 and is biased between flange 98and ball 68. Stem 80 is thus positioned to limit the distance that ball68 can be displaced from seat 70. In the configuration depicted in FIG.3, ball 68 is locked down and is not permitted to move. However, knob 64can be rotated to unthread tube 82 from socket 90, thereby retreatingstem 80 from ball 68. Retracting stem 80 within inlet passage 92 allowsfluids to pass through seat 70. Retracting stem 80 a small distancesuitable for thin fluids limits unnecessary travel of ball 68, therebyreducing wear of ball 68 and seat 70. Retracting stem 80 a furtherdistance away from seat 70 suitable for thick fluids allows the thickfluid to more easily pass through seat 70, thereby mitigating theformation of suction within pumping mechanism 18 (FIG. 1). After passingthrough seat 70, fluid travels through inlet passage 92, through inlets88 and into seat 79. Fluid pressure displaces ball 78 such that thefluid continues into body 74, travels through windows 86 and into outlet28, thus being positioned for dispensing with spray tip assembly 22(FIG. 1).

In one embodiment, tube 82 and socket 90 are provided with left-handthreads to provide an operator of device 10 with an intuitive interfacethat simulates “dialing down” to a thinner fluid. Specifically, turningknob 64 counter-clockwise inserts stem 80 further into passage 92 foruse with thinner fluids. Markings 95 on knob 64 can provide instructionas to which direction to rotate knob 64 for use with different fluids.Additionally, markings 95 on knob 64 can be aligned with marking 99 onhousing 24 to provide an operator a reference point for the position ofknob 64. Thus, numbers provided on knob 64 can be aligned with marking99 to indicate the operative position of stem 80 for use with fluids ofdifferent viscosities.

Although FIGS. 1-3 describe an adjustable ball stop with reference to aball valve, other types of check valves may be used. For example, thepresent invention may be used with poppet valves or flapper valves. Ballvalves, poppet valves and flapper valves each include a movable valvemember that engages with the adjustable stop of the present invention tolimit movement of the valve member from a valve seat. Likewise, FIGS.1-3 depict the present invention applied to an inlet check valve, butthe invention is also readily applicable to outlet check valves.Although FIGS. 1-3 depict one embodiment of adjusting ball travel in apump inlet check valve, other embodiments of adjustable stop 14 arecontemplated in the present invention, as are described with referenceto FIGS. 4-12.

FIG. 4 is a cross-sectional view of a second embodiment of adjustablestop 14 comprising detent set-point rod 100. Detent set-point rod 100 iscoupled to housing 102, which defines fluid flow path 104. Fluid flowpath 104 extends from inlet 104A to outlet 104B, and detent set-pointrod 100 is disposed between inlet 104A and outlet 104B to engage ball105. Detent set-point rod 100 includes rod 106, detent bar 108, handlebar 110 and seal 112. Rod 106 is inserted into cartridge 114, which isthreaded into counterbore 116B of bore 116A in housing 102. FIG. 5 is aperspective view of detent set-point rod 100 of FIG. 4 showing rod 106inserted into cartridge 114. Cartridge 114 includes slots 118A, 118B and118C, which are configured to engage detent bar 108 to limit a distancerod 106 can be displaced from seat 120 (FIG. 4).

As shown in FIG. 4, cartridge 114 is positioned around rod 106, such aswith a force fit. Thus, the position of rod 106 with respect tocartridge 114 remains fixed unless rod 106 is rotated, such as by usinghandle bar 110. Cartridge 114 is coupled to housing 102 via a threadedengagement such that the position of cartridge 114 is fixed with respectto housing 102. For example, cartridge 114 can be threaded intocounterbore 116B until flange 122 engages housing 102. Detent bar 108 isinserted through a cross- bore in rod 106 such as with an interferencefit connection. Rod 106 is positioned within bore 116A such that detentbar 108 is positioned within counterbore 116B between bore 116A andcartridge 114. Rod 106 is freely rotatable within bore 116A. Seal 112prevents fluid within fluid flow path 104 from escaping housing 102.

With reference to FIG. 5, slots 118A-118C have differing depths withrespect to end surface 124 of cartridge 114. Slot 118A is the shallowestsuch that the distance between end 126 of rod 106 and end surface 124 isthe greatest. Slot 118B is deeper than slot 118A, and slot 118C isdeeper than slot 118B such that the distance between end 126 and endsurface 124 diminishes as detent bar 108 is moved from slot 118A, toslot 118B to slot 118C. Detent bar 108 is moved between slots 118A, 118Band 118C manually by pushing rod 106 further into cartridge 114,rotating rod 106 to the desired position, and then pulling rod 106further out of cartridge 114 to engage with one of slots 118A, 118B and118C in a retracted position. A spring (not shown) may be used to biasrod 106 in the retracted position, such as a spring positioned betweenflange 122 and handle bar 110.

With reference to FIG. 4, as the position of rod 106 is adjusted usingdetent bar 108 and slots 118A-118C, end 126 of rod 106 is moved withrespect to seat 120, thereby changing the distance that ball 105 can bedisplaced from seat 120. In FIG. 4, ball 105 is shown in a solid lineengaged with seat 120, and in dashed lines engaged with rod 106. Whendetent bar 108 is inserted into slot 118A, as shown, the distancebetween end 126 and seat 120 is the least. Thus, very thin fluids willbe able to pass between seat 120 and ball 105. If detent bar 108 ismoved into slots 118B or 118C, thicker fluids will be able to moreeasily pass between seat 120 and ball 105. Cartridge 114 can be providedwith markings on flange 122 to indicate the position of slots 118A-118C.Handle bar 110 can be positioned relative to rod 106 in the sameorientation as detent bar 108. As such, handle bar 110 can be alignedwith markings on flange 122 to facilitate insertion of detent bar 108into slots 118A-118C.

FIG. 6 is a cross-sectional view of a third embodiment of adjustablestop 14 comprising threaded set-point rod 200. Threaded set-point rod200 is coupled to housing 202, which defines fluid flow path 204. Fluidflow path 204 extends from inlet 204A to outlet 204B, and threadedset-point rod 200 is disposed between inlet 204A and outlet 204B toengage ball 205. Threaded set-point rod 200 includes rod 206, hex head208, lock nut 210 and seal 212. Cartridge 214 is coupled to housing 202and engages with rod 206 to limit the distance ball 205 can be displacedfrom seat 220. Specifically, cartridge 214 is threaded into counterbore216B, while rod 206 is threaded into cartridge 214 to extend throughbore 216A. Seal 212 prevents fluid within fluid flow path 204 fromescaping housing 202. Using hex head 208, the position of rod 206relative to cartridge 214 can be adjusted at the threaded engagement tochange a distance between end 226 of rod 206 and seat 220. In FIG. 6,ball 205 is shown in a solid line engaged with rod 206, and in dashedlines engaged with seat 220. Thus, adjustable stop 14 can be configuredto permit fluids of different viscosities to more optimally pass betweenseat 220 and ball 205. The threaded engagement between rod 206 andcartridge 214 allows for an infinite adjustment of the travel of ball205 between a maximum and a minimum distance, produced by the extremesof the threaded engagement. Once rod 206 is adjusted to the desiredposition, lock nut 210 can be threaded down on rod 206 to engage flange222 and lock the position of rod 206 relative to cartridge 214.

FIG. 7 is a cross-sectional view of a fourth embodiment of adjustablestop 14 having rotatable ball stop 300. Rotatable ball stop 300 iscoupled to housing 302, which defines fluid flow path 304. Fluid flowpath 304 extends from inlet 304A to outlet 304B, and rotatable ball stop300 is disposed between inlet 304A and outlet 304B to engage ball 306.Ball 306 engages seat 308. Rotatable ball stop 300 includes rod 310,handle 312 and variable stop 314. Rod 310 is joined to housing 302 usingcartridge 316, which is threaded into counterbore 318B of bore 318A.Seal 320 is positioned within cartridge 316 around rod 310 to preventfluid from within flow path 304 from leaving housing 302.

Rod 310 extends through cartridge 316 in a rotatable fashion. In oneembodiment, rod 310 is threaded into cartridge 316. In otherembodiments, rod 310 may be freely rotatable within cartridge 316 andretained by step 322 on rod 310 that engages a corresponding lip formedby cartridge 316 at bore 318A. Rod 310 includes first portion 310A,second portion 310B, third portion 310C and fourth portion 310D. Firstportion 310A extends from an exterior of housing 302 to provide foradjustment of variable stop 314 external of housing 302 via handle 312.Second portion 310B is coupled to housing 302, such as through a directthreaded engagement or through threaded engagement with cartridge 316.Third portion 310C extends into flow path 304 so as to position variablestop 314 relative to ball 306. Fourth portion 310D extends into housing302 to support rod 310. Fourth portion 310D may be simply supported inan un-threaded bore. In other embodiments, fourth portion 310D may beomitted such that third portion 310C is cantilevered from housing 302.Handle 312 may be releasably attached to rod 310, such as by using setscrew 323, to facilitate assembly of rod 310 to housing 302 andcartridge 316.

Ball 306 is positioned in flow path 304 to interrupt flow of fluidbetween inlet 304A and 304B. In the depicted embodiment, flow path 304extends linearly along axis A₁ between inlet 304A and outlet 304B. Thus,seat 308 includes an opening for ball 308 that is concentric with axisA₁. A spring (not shown) may be used to bias ball 306 against seat 308.A pressure differential between inlet 304A and outlet 304B causes ball306 to disengage seat 308, thereby permitting fluid flow. The distancethat ball 306 is permitted to move away from seat 308 is determined byvariable stop 314. In the embodiment shown, rod 310 extends across flowpath 304 along axis A₂ that is generally perpendicular to axis A₁ offlow path 304. Variable stop 314 extends from third portion 310C toengage ball 306. Variable stop 314 includes one or more features thatextend radially from rod 310 and axis A₂ to change a distance betweenvariable stop 314 and seat 308 along axis A₁, thereby changing thedistance ball 306 can move away from seat 308. For example, variablestop 314 may provide a plurality of discrete positions for ball 306, ormay provide an unlimited number of positions for ball 306.

FIGS. 8A-8C show a first embodiment of rotatable ball stop 300 of FIG. 7wherein variable stop 314 comprises offset pin 324. Ball 306 sitsagainst seat 308 in a closed position. Third portion 310C of rod 310 isfixed relative to seat 308 via coupling to housing 302 (FIG. 7). Offsetpin 324 extends through third portion 310C, which extends along axis A₂(FIG. 7), such that first portion 324A extends a first radial distancefrom rod 310 and second portion 324B extends a second radial distancefrom rod 310 that is greater than the first distance. In FIG. 8A thirdportion 310C is rotated such that first end 324A of pin 324 facestowards ball 306. First end 324A extends from rod 310 such that distanced₁ is provided to ball 306. Thus, ball 306 can only be displaceddistance d₁ from seat 308 to permit fluid through seat 308. If thickerfluids are needed to be passed through seat 308, third portion 310C canbe rotated such that pin 324 is perpendicular to axis A₁ (FIG. 7)extending through seat 308. Ball 306 is thus permitted its maximumtravel distance d₂ between seat 308 and rod 310. If thinner fluids areneeded to be passed through seat 308, third portion 310C can be rotatedsuch that second end 324B of pin 324 faces towards ball 306. Second end324B extends from rod 310 such that distance d₃ is provided to ball 306.Thus, ball 306 can only be displaced distance d₃ from seat 308 to permitfluid through seat 308. The embodiment of FIGS. 8A-8C provide threedistinct ball travel distances for thick, thin and intermediate fluids,as are determined by different radial dimensions of offset pin 324relative to axis A₂ within rod 310. Variable stop 314 may have othershapes that permit additional levels of ball travel distances.

FIGS. 9A-9C show a second embodiment of rotatable ball stop 300 of FIG.7 wherein variable stop 314 comprises cam 326. Ball 306 sits againstseat 308 in a closed position. Third portion 310C of rod 310 is fixedrelative to seat 308 via coupling to housing 302 (FIG. 7). Cam 326surrounds third portion 310C, which extends along axis A₂ (FIG. 7), suchthat lobe 326A extends a first radial distance from rod 310 and boreportion 326B extends a second radial distance from rod 310 that is lessthan the first radial distance. In FIG. 9A third portion 310C is rotatedsuch that lobe 326A of cam 326 faces towards ball 306. Lobe 326A extendsfrom rod 310 such that distance d₁ is provided to ball 306. Thus, ball306 can only be displaced distance d₁ from seat 308 to permit very thinfluid through seat 308. If thicker fluids are needed to be passedthrough seat 308, third portion 310C can be rotated one-hundred-eightydegrees such that bore portion 326B faces towards ball 306. Ball 306 isthus permitted its maximum travel distance d₂ between seat 308 and rod310. The embodiment of FIGS. 9A and 98B provide two extreme ball traveldistances for thin and thick fluids, respectively. If fluids ofintermediate viscosity are needed to be passed through seat 308, thirdportion 310C can be rotated to rotate cam 326 through an infinite numberof intermediate positions for fluids having different levels ofviscosity. In FIG. 3C, cam 326 is positioned such that lobe 326A andbore portion 326B extend perpendicularly to axis A₁ (FIG. 7) extendingthrough seat 308. As such, curved side 326C of cam 326 faces towardsball 306. Curved side 326C has a thickness greater than bore portion326B, but smaller than lobe 326A. Thus, ball 306 can only be displaceddistance d₃ from seat 308 to permit fluid through seat 308. Curved side326C has a shape that is arcuate so as to engage ball 306 at differentcircumferential positions along the surface of ball 306 while ball 306is at different axial positions along axis A₁, thereby providing a rangeof ball travel distances. The different axial positions of ball 306along axis A₁ are determined by cam 326 having different radialdimensions relative to axis A₂ along which rod 310 extends.

FIG. 10 is a cross-sectional view of a fifth embodiment of adjustablestop 14 comprising push-pull bar 400. Push-pull bar 400 is coupled tohousing 402, which defines fluid flow path 404. Push-pull bar 400extends across fluid flow path 404 to engage a ball 406 disposed influid flow path 404. Push-pull bar 400 includes first end 408A, secondend 408B and middle section 408C. First end 408A is inserted intocartridge 410A and includes flange 412 to retain spring 414. Cartridge410A is threaded into housing 402 and seal 416 prevents fluid fromwithin fluid flow path 404 from leaking out of housing 402. Second end408B is inserted into cartridge 410B and is rotatably coupled to lockingcam 418 at pin 420. Cartridge 410B is threaded into housing 402 and seal422 prevents fluid from within fluid flow path 404 from leaking out ofhousing 402. Middle section 408C includes step 424, which is positionedopposite ball 406.

Spring 414 biases push-pull rod 400 toward the left with reference tothe orientation of FIG. 10. Cam 418 includes arcuate surface 426 thatengages housing 402 and that extends along arc that varies in distancefrom pin 420. Cam 418 can be rotated at pin 420 using handle 428 pullpush-pull rod 400 toward the right with reference to the orientation ofFIG. 10. With cam 418 rotated so that handle 428 is down (with referenceto the orientation of FIG. 10), step 424 is positioned in-line with ball406 with reference to fluid flow path 404. Thus, ball 406 can only moveupward (with reference to the orientation of FIG. 10) until it engagesstep 424. Can 418 can be rotated so that handle 428 is upward (withreference to the orientation of FIG. 10) to pull rod 400 and step 424away from alignment with ball 406 so that ball 406 can move upward anadditional distance equal to the thickness of step 424. Thus, the travelof ball 406 can be adjusted to improve performance of a pump for fluidsof different viscosities. In other embodiments, middle section 408C caninclude multiple steps of different thicknesses to provide a pluralityof discrete ball travel increments. In other embodiments, middle section408C can be tapered, such as over a conical section, to provide aplurality of intermittent levels of ball travel between two extremelevels.

FIG. 11 is a cross-sectional view of a sixth embodiment of adjustablestop 14 having cartridge 500 with detent position control 502. In theembodiment of FIG. 11, adjustable stop 14 comprises a rotatable shaftsimilar to that of FIG. 7. Specifically, rod 504 extends into housing506 to position variable stop feature 507 relative to a valve ball (notshown) to adjust ball travel. Variable stop feature 507 comprises a pinor cam, such as is described with reference to FIGS. 8A-9C. Rod 504 issecured to housing 506 via cartridge 500, which is threaded into bore508. Rod 504 extends through bore 510 in cartridge 500. Seal 512prevents fluid from within housing 506 escaping through bores 508 and510. Rod 504 also includes flange 514, which is disposed within knob516. Knob 516 includes cavity 518, slot 519 that surrounds flange 514,bore 520 through which rod 504 extends, spring 522 that biases knob 516toward cartridge 500, and grip flange 523. Detent position control 502includes detent 524 and detent hole 526.

Detent 524 is sized to fit into detent hole 526 to limit rotation ofknob 516 relative to cartridge 500. FIG. 12 is a top view of cartridge500 of FIG. 11 showing different detent holes 526. As shown in FIG. 12,detent holes 526 are distributed in a circular array centered on bore510 in a surface of cartridge 500 that faces towards knob 516 and detent524. As mentioned, spring 522 pushes knob 516 toward cartridge 500 bypushing against cavity 518 and flange 514 so that detent 524 is pushedinto one of holes 526. As such, variable stop feature 507 is locked intoone rotational position on rod 504 relative to a ball seat of a ball forwhich variable stop feature 507 is configured to limit movement. Therotational position of variable stop feature 507 can be adjusted bypulling on grip flange 523 to retract knob 516 away from cartridge 500,rotating knob 516 on rod 504 so that detent 524 aligns with another ofholes 526 in the circular array, and releasing grip flange 523 so thatdetent 524 seats within one of holes 526. As discussed with reference toFIGS. 8A-9C, a variable stop feature can be repositioned to change theinlet opening size of a valve to optimize entry of fluids with differentviscosities into a pump. Detent position control 502 allows the variablestop feature to be held in place such that the inlet opening size doesnot drift or change during operation of the pumping system. In anotherembodiment of the invention, detent holes 526 can be provided withmarkings that indicate the position of variable stop feature 507relative to a ball seat, or that indicate a desired position of knob 516for fluids of different viscosities.

While the invention has been described with reference to exemplaryembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiments disclosed, but that theinvention will include all embodiments falling within the scope of theappended claims. For example, various components of system 10 and meltsystem 30 can be sized, shaped, and configured differently than asillustrated as appropriate for a given application.

1. A check valve comprising: a housing; a fluid passage extendingthrough the housing; a seat disposed in the fluid passage; a valvemember positioned in the passage to engage the seat; and a stopextending through the housing to engage the valve member, the stopcomprising: a rod joined to the housing and having a first endterminating outside of the housing; wherein the stop is accessible fromoutside the housing to adjust a gap between the rod and the valvemember, to thereby adjust a distance the valve member can travel fromthe seat.
 2. The check valve of claim 1, wherein the rod is joined tothe housing at a threaded coupling.
 3. The check valve of claim 2,wherein: the rod extends obliquely to an axis extending through theseat; and a second end of the rod terminates in the fluid passage,engages the valve member, and defines the gap and thus the distance thevalve member can travel from the seat.
 4. The check valve of claim 3,wherein the threaded coupling comprises: a cartridge threaded into thehousing; and a bore in the cartridge through which the rod extends. 5.The check valve of claim 4, wherein the threaded coupling includes: alock nut that limits rotation of the rod relative to the cartridge. 6.The check valve of claim 4, wherein the threaded coupling comprises: adetent that limits rotation of the rod relative to the cartridge.
 7. Thecheck valve of claim 6, wherein the detent comprises: a detent barextending from the rod; and a slot extending into the cartridge from anend surface of the cartridge, the slot configured to receive the detentbar to define the gap between the rod and the valve member.
 8. The checkvalve of claim 7, wherein the slot comprises a plurality of slots havingvarying depths with respect to the end surface of the cartridge.
 9. Thecheck valve of claim 8, wherein the stop further includes: a markervisible from an exterior of the housing to provide an indication of thelocation of the stop relative to the seat; and a handle graspable froman exterior of the housing, the handle selected from the groupconsisting of a knob, a rod and a locking cam.
 10. The check valve ofclaim 2, wherein the rod extends perpendicularly to an axis extendingthrough the seat.
 11. The check valve of claim 10, wherein the rodfurther comprises: a second section extending through the housing; and athird section extending into the fluid passage to engage the valvemember.
 12. The check valve of claim 11, wherein the third section ofthe rod includes a cam.
 13. The check valve of claim 11, wherein thethird section of the rod includes a pin extending from the rod, the pincomprising: a first end extending from the rod a first radial distance;and a second end extending from the rod a second radial distance greaterthan the first radial distance.
 14. The check valve of claim 11, whereinthe rod further comprises: a fourth section extending from the thirdsection and into the housing.
 15. The check valve of claim 14, whereinthe third section extending into the fluid passage includes: a taperedportion positioned across from the valve member.
 16. The check valve ofclaim 14, wherein the third section extending into the fluid passageincludes: a stepped portion positioned across from the valve member. 17.A pump comprising: a housing; a fluid passage extending through thehousing from an inlet to an outlet; a pump mechanism disposed within thehousing and configured to pump fluid from the inlet to the outlet; acheck valve disposed in the fluid passage, the check valve comprising: aseat; a valve member separable from the seat over a gap; and a rodadjustably coupled to the housing, the rod comprising: a first sectionextending from an exterior of the housing; a second section terminatingin the fluid passage and configured to engage the valve member anddefine the gap and thus the distance the valve member can travel fromthe seat.
 18. The pump of claim 17, further comprising: a cartridgeattached to the housing; and a bore extending through the cartridge, therod extending through the bore; wherein the rod extends obliquely to anaxis extending through the seat.
 19. The pump of claim 18, furthercomprising: a detent bar extending from the rod; and a plurality ofslots having varying depths extending into the cartridge from the endsurface of the cartridge, the plurality of slots configured to receivethe detent bar to define the gap between the rod and the valve member.20. The pump of claim 18, further comprising: a lock nut disposed on thecartridge and configured to limit rotation of the rod relative to thecartridge.